This invention relates to a solder bath apparatus and, more particularly, to a solder bath apparatus adapted to form an overflow layer of molten solder in which an article to be soldered is dipped.
It is known in the art to use the so-called flow-dip type solder bath having an inner vessel provided within an outer vessel which contains molten solder. The molten solder within the outer vessel is fed to the inner vessel by a pump or other suitable means to form an overflow layer of molten solder over the inner vessel. An article to be soldered, like a printed circuit board, is dipped in the overflow layer to effect the necessary soldering.
FIG. 1 of the accompanying drawings shows one example of the conventional flow-dip type solder bath as mentioned above, in which the reference numerals 1 and 2 denote the outer and inner vessels, respectively. Connected to the bottom of the inner vessel 2 is one end of a conduit 4 which is provided with an opening 7 at the other end thereof. A rotating propeller 5 which is driven by a motor 6 is provided within the conduit 4 at a position over the aforementioned opening 7.
As the propeller 5 is rotated by the motor 6, the molten solder within the outer vessel 1 is sucked into the conduit 4 and fed into the inner vessel 2, the molten solder being caused to overflow through an upper opening 3 of the inner vessel 2 in the radial directions as shown in FIG. 2 to return to the outer vessel 1.
An article to be soldered, for instance a printed circuit board 8, is dipped in the overflowing layer of the melt to effect the necessary soldering treatment. In this case, the overflowing layer of the melt runs in the radial directions as shown in FIG. 2, so that it becomes difficult to effect satisfactory soldering due to stagnation of solder oxides, formed by contact with air, in the center portion S. In a case where the printed circuit board 8 is dipped in the overflowing layer while being continuously moved in the horizontal direction, the soldering effect differs from one to the other part of the board since the flow of the melt is not unidirectional. In addition, when the printed circuit plate is removed from the soldering plane, unnecessary solder tends to remain on the printed circuit board.